Size‐selective colloidal‐gold localization in transmission X‐ray microscopy

Abstract

Key words. colloidal gold, image analysis, soft X-ray microscopy. SummaryColloidal gold is a useful marker for functional-imaging experiments in transmission X-ray microscopy. Due to the low contrast of gold particles with small diameters it is necessary to develop a powerful algorithm to localize the single gold particles. The presented image-analysis algorithm for identifying colloidal gold particles is based on the combination of a threshold with respect to the local absorption and shape discrimination, realized by fitting a Gaussian profile to the identified regions of interest. The shape discrimination provides the possibility of size-selective identification and localization of single colloidal gold particles down to a diameter of 50 nm. The image-analysis algorithm, therefore, has potential for localization studies of several proteins simultaneously and for localization of fiducial markers in X-ray tomography.

High‐resolution compact X‐ray microscopy

“…Finally, we note that the microscope can be used for high‐resolution imaging with chemical contrast in addition to the natural contrast, employing colloidal gold markers. Stollberg et al (2007), recently demonstrated an image‐analysis algorithm for the size‐selective localization of single colloidal‐gold particles in cell like structures. Gold particles down to a size of 50 nm could clearly be identified and localized by this algorithm.…”

Transmission X‐ray microscopy for full‐field nano imaging of biomaterials

“…6). Gold immunolabeling and quantum dots (Stollberg et al, 2007) can also help to image structures bound to specific functional groups.…”

“…No staining is required for imaging with either TXM or microprobe, thus, the biochemistry of the original samples can be preserved. However, immunolabeling, e.g., with gold nanoparticles can be used to identify regions of biological tissue with specific proteins or functional groups (Stollberg et al, 2007) for further insight into physiology.…”

“…Improved data processing will include automated alignment and reconstruction of tomographic data sets including mosaic tomography and segmentation of tomographic data sets by attenuation coefficient, which is now often done by hand. Algorithms can be used to locate specific features such as smaller nanoparticles bound to physiologically functional groups (Stollberg et al, 2007). In addition, as more users grow familiar with the technique and perfect the preparation of samples (which although relatively simple can require significant forethought and trial imaging), even more useful and efficient data will emerge from TXM imaging.…”

Analysis of extreme ultraviolet microscopy images of patterned nanostructures based on a correlation method

“…These techniques have been successfully employed to enhance contrast in images obtained with an SXR microscope [9]. Image analysis can also be used to map the location of markers such as gold nanoparticles, commonly used in biological imaging applications [10], or to determine the position of latex nanospheres in three dimensions [11]. In general, these tools are based on a wavelet analysis.…”